Heat spreader with vapor chamber

ABSTRACT

A heat spreader includes a base with a cavity defined therein and a cover mounted on the base to thereby hermetically seal the cavity of the base. A predetermined quantity of working liquid is contained in the cavity. The heat spreader further includes a first wick structure formed on an inner surface of the base, a second wick structure formed on an inner surface of the cover and a third wick structure embedded in the first wick structure. The first and second wick structures are made of metal mesh, carbon nanotube array or bundle of fibers and the third wick structure is made of sintered metal powder. In use, the third wick structure is positioned corresponding to a heat generating electronic component.

BACKGROUND

1. Technical Field

The present disclosure relates to heat spreaders and, more particularly, to a heat spreader with a vapor chamber having good heat transfer capability and with small thickness.

2. Description of Related Art

Electronic components, such as central processing units (CPUs) comprise numerous circuits operating at high speeds and generating substantial heat. Under most circumstances, it is necessary to cool the CPUs to maintain safe operating conditions and assure that the CPUs function properly and reliably. In the past, various approaches have been used to cool electronic components.

A heat spreader with a vapor chamber is usually used to help heat dissipation for electronic components. The heat spreader generally includes a base, a cover mounted on the base and a sealed chamber defined between the base and the cover. Moderate working liquid is contained in the chamber. The base has a wick structure spreading on the whole inner surface thereof, and the cover has a wick structure spreading on the whole inner surface thereof, too. During operation, the base absorbs heat from the electronic components, and the working liquid is heated into vapor in the chamber. The vapor flows towards the cover and dissipates the heat to the cover, then condenses into liquid and returns back to the base by the drive (i.e., capillary action) of the wick structures to continue a phase-change cycle.

However, different types of wick structures have different capability, e.g. sintered metal powder has good evaporating efficiency but large flow impedance to the working liquid; comparatively, metal mesh has less flow impedance but worse evaporating efficiency. This will adversely affect heat transfer efficiency of the heat spreader.

What is needed, therefore, is a heat spreader with a vapor chamber which has good heat transfer capability.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is an assembled, isometric view of a heat spreader in accordance with an embodiment of the disclosure.

FIG. 2 is an exploded view of the heat spreader of FIG. 1.

FIG. 3 is an inverted, exploded view of the heat spreader of FIG. 1.

FIG. 4 is a cross-section view of the heat spreader of FIG. 1, taken along a line IV-IV thereof.

FIG. 5 is an enlarged view of a part V of the heat spreader of FIG. 4.

DETAILED DESCRIPTION

Referring to FIGS. 1-2, a heat spreader in accordance with the disclosure comprises a base 10 with a cavity (not labeled) defined therein and a cover 20 mounted on the base 10 to hermetically seal the cavity of the base 10, thereby defining a chamber 12 enveloped by the cover 20 and the base 10. A predetermined quantity of working liquid, such as water, alcohol, olefin and so on is contained in the chamber 12 for transferring heat from the base 10 to the cover 20 by a phase change of the working liquid. The chamber 12 is evacuated for easy evaporation of the working liquid. The heat spreader further comprises a first wick structure 30 attached to an inner surface of the base 10, a second wick structure 40 attached to an inner surface of the cover 20 and a third wick structure 50 formed on a central portion of the inner surface of the base 10 and surrounded by the first wick structure 30.

Also referring to FIG. 3, the base 10 and the cover 20 are both made of metal with good heat conductivity, such as aluminum, copper, or alloys thereof. The base 10 has a bottom (outer) face for thermally contacting a heat-generating component (not shown) to absorb heat produced by the heat-generating component. Generally, the heat-generating component is attached to a center portion of the bottom face of the base 10. The base 10 has a flange 14 circumferentially extending outwardly and horizontally from a top of the base 10. The flange 14 of the base 10 hermetically engages with a circumference of a bottom (inner) face of the cover 20.

Also referring to FIGS. 4-5, the first wick structure 30 spreads on the inner surface of the base 10 and faces the cover 20. A rectangular, hollow receiving portion 32 for receiving the third wick structure 50 is defined in the first wick structure 30 at a position corresponding to the central portion of the base 10. In other words, the receiving portion 32 is an opening extending through a central portion of the first wick structure 30. The first wick structure 30 can be selected from structures having low flow impedance such as metal mesh, carbon nanotube array, bundle of fibers and so on.

The second wick structure 40 spreads on the inner face of the cover 20 and has a rectangular configuration. A circumference of a bottom of the second wick structure 40 tightly engages with a circumferential end of the first wick structure 30, which is oriented upwardly. Furthermore, pores in the circumference of the bottom of the second wick structure 40 and pores in the circumferential end of the first wick structure 30 communicate with each other; therefore, the working liquid can flow smoothly from the second wick structure 40 to the first wick structure 30. The second wick structure 40 can be selected from structures having low flow impedance capability such as metal mesh, carbon nanotube array, bundle of fibers and so on.

The third wick structure 50 has a configuration identical to that of the receiving portion 32 of the first wick structure 30, thereby being fitly received in the receiving portion 32 of the first wick structure 30. The third wick structure 50 directly contacts the inner face of the base 10. A circumferential end of the third wick structure 50 tightly engages with the first wick structure 30, whereby pores in the first and third wick structures 30, 50 communicate with each other. The third wick structure 50 can be selected from structures having good evaporating efficiency such as sintered metal powder. Furthermore, the third wick structure 50 can be selected from other types of wick structures having a large evaporating surface, more specifically, a large surface area to volume ratio.

During operation of the heat spreader, the heat-generating component is attached to the base 10 under the third wick structure 50, and the base 10 absorbs the heat produced by the heat-generating component. The working liquid saturated in the third wick structure 50 is heated into vapor. The vapor escapes from the third wick structure 50, and is quickly diffused into the whole chamber 12 of the heat spreader. When the vapor contacts the second wick structure 40 and the cover 20, it gives out heat and condenses into liquid. The condensed working liquid then flows back to the third wick structure 50 through second wick structure 40 and the first wick structure 30 which connects with the second wick structure 40 and the third wick structure 50.

As mentioned above, the third wick structure 50 having good evaporating efficiency is positioned on the inner surface of the base 10, particularly on the center portion of the inner surface of the base 10 corresponding to the heat-generating component. Meanwhile, the first wick structure 30 and the second wick structure 40 having low resistance to the working liquid are placed allover the inner surfaces of the heat spreader except where the third wick structure 50 occupies, for transferring the condensed working liquid. Therefore, the working liquid saturated in the third wick structure 50 can be quickly heated into vapor to bring the heat to the second wick structure 40 and the cover 20, and the condensed working liquid at the second wick structure 40 and the cover 20 can be effectively and quickly transferred back to the third wick structure 50 through the second wick structure 40 and the first wick structure 30, whereby the heat transfer efficiency of the heat spreader is improved. Additionally, because the third wick structure 50 is wholly received in the receiving portion 32 of the first wick structure 30, the heat spreader can be designed to have a small thickness since less space is needed for accommodating the first and third wick structures 30, 50, which in combination has a structure of a single layer.

It is believed that the disclosure and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being exemplary or exemplary embodiments of the invention. 

1. A heat spreader comprising: a base; a cover mounted on the base thereby defining a chamber enveloped by the base and the cover; a working liquid contained in the chamber; a first wick structure spreading on an inner surface of the base and defining a receiving portion in the first wick structure; a second wick structure spreading on an inner surface of the cover; and a third wick structure embedded in the receiving portion of the first wick structure.
 2. The heat spreader as claimed in claim 1, wherein the first wick structure connects with the second wick structure.
 3. The heat spreader as claimed in claim 2, wherein pores in the first wick structure and pores in a circumference of the second wick structure are communicated with each other.
 4. The heat spreader as claimed in claim 1, wherein a circumference of the third wick structure connects with the first wick structure, the third wick structure being wholly received in the receiving portion of the first wick structure.
 5. The heat spreader as claimed in claim 1, wherein the first wick structure and the second wick structure are structures having low flow impedance.
 6. The heat spreader as claimed in claim 5, wherein the first wick structure and the second wick structure each are selected from one of metal mesh, carbon nanotube array and bundle of fibers.
 7. The heat spreader as claimed in claim 1, wherein the third wick structure is formed by sintered metal powder.
 8. The heat spreader as claimed in claim 1, wherein the third wick structure is located corresponding to a central portion of the base, the first wick structure being the same type wick structure as the second wick structure, and the third wick being another type wick structure different from the first wick structure.
 9. The heat spreader as claimed in claim 1, wherein a flange circumferentially extends outwardly and horizontally from a top of the base, and the flange hermetically engages with a circumference of the cover.
 10. A heat spreader comprising: a base with a cavity defined therein; a cover hermetically covering the base; a working liquid contained in the cavity; a first wick structure attached on an inner surface of the base; a second wick structure attached on an inner surface of the cover; and a third wick structure formed on a central portion of the inner surface of the base and surrounded by the first wick structure.
 11. The heat spreader as claimed in claim 10, wherein a circumference of the second wick structure connects with the first wick structure.
 12. The heat spreader as claimed in claim 10, wherein a circumference of the third wick structure tightly contacts with the first wick structure.
 13. The heat spreader as claimed in claim 10, wherein the first wick structure is selected from one of metal mesh, carbon nanotube array and bundle of fibers.
 14. The heat spreader as claimed in claim 10, wherein the second wick structure is selected from one of metal mesh, carbon nanotube array and bundle of fibers.
 15. The heat spreader as claimed in claim 10, wherein the third wick structure is formed by sintered metal powder.
 16. The heat spreader as claimed in claim 10, wherein a flange circumferentially extends outwardly from a top of the base, and the flange hermetically engages with a circumference of the cover.
 17. The heat spreader as claimed in claim 10, wherein the first wick structure and the third wick structure together form a structure of a single layer. 